Oxidation of Zirconium Diboride with Tungsten Carbide Additions

The oxidation resistance of zirconium diboride (ZrB 2 ) ceramics with tungsten carbide (WC) additions was studied. ZrB 2 ceramics, nominally pure and with WC additions of 4, 5, and 6 mol%, were densified by pressureless sintering. During heating, the WC that was added to the ceramic dissolved into the ZrB 2 matrix, forming a solid solution. Oxidation behavior was evaluated using isothermal furnace oxidation at 1500°C and 1600°C. The presence of tungsten reduced both the weight gain and oxide scale thickness compared with nominally pure ZrB 2 . After oxidation at 1600°C for 3 h, the thickness of the ZrO 2 outer scale was reduced from 4.7 mm for nominally pure ZrB 2 to 0.5 mm for the ceramic containing 6 mol% WC. Analysis showed that WC additions improved the oxidation resistance of ZrB 2 by changing the morphology of the zirconia scale formed during oxidation.

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